This invention is related to metering of fluids and, in particular, to a meter suitable for use in domestic gas metering.
European patent application No. 86309946.1 (THORN EMI plc) filed Dec. 19, 1986 and published on Oct. 7. 1987 as publication No. 0239,703, describes an example of a flow sensing device comprising a micro-engineered cantilevered beam fabricated on a semiconductor substrate and means sensitive to a characteristic of the beam which is indicative of fluid flow relative to the beam. The sensitive means may be a capacitive displacement sensor including a first electrode at the free end of the beam and a second electrode on the substrate below the first electrode, the sensor responding to a deflection of the beam relative to the substrate due to fluid flowing past the beam.
It is desirable that a micro-engineered cantilevered beam flow sensor (referred to hereinafter as a "microbeam flow sensor") should be positioned in a flowing fluid for a period of about 20 years and, over this period, contamination, both particulate and film, changes in fluid composition, and also drift due to the analogue nature of the device are likely to occur and to affect the performance of the sensor.